This invention relates to the measurement of the level of a liquid in a vessel. More particularly, this invention relates to the use of microwave energy absorption to measure the level of a liquid in a vessel. More particularly, this invention relates to the use of microwave energy absorption to indicate small changes in the level of a liquid in a vessel for control of the level.
The prior art is replete with methods for measuring the level of a liquid within a vessel using dip-sticks, floats, pressures, sonics and radioactivity. Microwaves have been restricted in use to communications, to determination of variations in dielectrics, and to determination of the moisture content of various materials. The latter usage and the present invention both utilize the principle of absorption of microwave energy by liquids. However, microwaves have not been used as a means to detect liquid level in a vessel before this invention. The use of microwaves to measure liquid level is particularly useful when it is desired to detect very small changes in the liquid level.